The transverse force that can be produced by your monoblock surface is given by the formula known to all aerodynamicists:

F = 0.5 ρ * s * v² * cL

If the Reynolds Number is only 800,000, then cL is maximum when the A.o.A is about 18 degrees .

This is what the NACA report n° 610 shows, fig 4, for example:

This angle is gived for an infinite aspect ratio.

Whereas the rudder has an aspect ratio of about 4.

l must then add the angle induced under Prandtl's theory discovered in 1911

Induced angle (radians) = cL / π*A Hence 4 degrees for cL = 1.2

So, 22 degrees gives the maximum result and 35 degrees gives clearly less (observe the NACA curve)

Have the laws of aerodynamics been repealed recently?